Humidity-responsive switch



Feb. 13, 1945, G. w? CHSE 2,369,215

HUMIDITY-RESPONSIVE SWITCH 21194 May 21. 194;

, ate circuit controls.

Patented Feb. 13, 1945 UNITED STATES PATENT OFFICE HUMIDITY -RESPON SIV E SWITCH George W. Crise, Columbus, Ohio, assignor to Crise Electric Manufacturing Company, Golumbus, Ohio, a corporation of Ohio Application May 27, 1943, Serial No. 488,707

6 Claims.

ing or'other enclosures with atmospheres having a desired range of relative humidity. Such switches or controls are known commercially as humidostats.

Many humidostats are now constructed tdemploy. as motivating elements various materials which contract, elongate or flex in a predetermined manner when in contact with atmospheres varying in their water vapor content, so that their variations in positions or condition, in response to humidity changes, may be used to actu- Such prior devices in their commercial forms do not give complete operational reliability, are quite likely to become out of order and, moreover, are relatively expensive and complicated in construction.

Accordingly, it is an object of the present invention to provide a simple and rugged humidostat, wherein is embodied a novel motivating element in the form of an air permeable receptacle, the latter containing a body of water vapor absorbing material, such as a deliquescent salt, the receptacle being movably supported within the casing so that when its effective weight changes, as a result of the absorption or release of moisture by the absorbing material contained therein, the same will be caused to assume different operathe numeral l designates the casing of my improved humidostat. This casing preferably comprises a base section 2 having a flat vertical rear surface to render the same suitable for applica tion to a room wall. Also, the casing includes a removable cover section 3 for the purpose of closing the mechanism disposed Within the internal chamber 4 of the .base section. At its sides, the base section is formed with screw-receiving recesses 5, the latter having arcuate walls 5. The casing sections may be formed from any suitable molded plastic having insulating properties, such as Bakelite, Tenite or the like.

tive positions within the casing, this movement of the receptacle being utilized to control the automatic opening and closing of associated cir-i cuit making and breaking contacts. j

It is another object of the invention to provide a humidostat capable of handling substantial amounts of electric current without objectionable differential and one which may be of such-design as to be either temperature compensating or enmay unafiected by thermal changes, as desired.

For a further understanding of the invention,

reference is to be had to the following description and the accompanying drawing, wherein:

Fig. 1 is a iront elevational view of a humido-I ,phere.

Adjacent to the bottom of the chamber 4, the walls of the base section are inwardly grooved as at I. These grooves are adapted to receive the ends of a bimetallic flexible strip 8, the latter being so formed that its central region will flex upwardly when the same is warmed. Adjacent to the top of the chamber 4, the base section is provided with inwardly extending grooves 9, which receive the ends of a bimetallic strip Hi, the latter, being so formed that when it is warmed, its central region will sag or flex downwardly.

Positioned vertically in the chamber 4 and having the ends thereof suitably secured to the 'strips'8 and I0 is a cylindrical receptacle H, the

foraminous, in order that the same may berendered permeable to the environmental atmos Preferably the receptacle is of such size that its vertical walls are disposed immediately adjacent to the arcuate walls 6, so that the latter may act as guides in the vertical movement of the receptacle in response to changes in its effective weight. It will be evident that the action of my humidostat is based on the fact that when the receptacle H is filled" with a desired moisture absorbent material, the efiective weight of the same changes rapidly withchanges in humidity of the surrounding air. When the relative humidity is high, the total weight of the receptacle including its contents is greater than when the humidity ratio is lower.

Carried by the top of the bimetallic strip i0 is a circular disk-like magnet |3,'the same being of high permeability type and formed of such materials as an aluminum-nickel-cobalt alloy. This magnet is adapted to attract, and is arranged in vertical registration with, an armature Referring more particularly to the drawing, N which may partake oi. the form or an iron washer. For convenience in assembly and mounting, this washer is carried by the under side of a resilient metallic strip 15, the ends of the latter being disposed in grooves l formed in the upper end of the chamber 4. The upper surface of the magnet 13 is provided with an upstanding contact in the form or a stud l1 and likewise the armature I4 is provided with a. complemental depending contact I8 01 post or studlike form.

Relative adjustment between the magnet and the armature may be effected by the provision of an adjusting screw IS. The shank of this screw passes through a threaded bore provided in the upper end of the base section 2 of the casing and the lower end of the screw bears on the center region of the strip IS. The upper end of the screw, which projects above the casing, has fastened thereto an adjustin knob 20, the perimeter of which may be suitably graduatedor calibrated for reference with a fixed index point to provide an external indication of the operative setting of the humidostat.

Th magnet i3 and the annature it are pro vided in order to permit the contacts i1 and In to handle a substantial current. That is, when the contacts are in engagement, the attraction of the magnet for the armature is at its greatest value, thus maintaining the contacts in close association and held so in spite of minor forces on the part of the receptacle which may tend to break such engagement and cause undesired fluctuation in the electric circuit associated with the humidostat. However, to overcome undesired lag in the opening of the associated circuit, caused by the sticking action of the magnet, the spring strips 8 and ID are of bimetallic construction. The upper strip I0 has disposed in close proximity thereto, in a preferred form of the invention, a resistance wire 2|, which becomes heated upon the passage of electric current therethrough. By supplying localized heat to the strip i0 independently of that of the atmosphere, the same will be caused to flex to separate the contacts, independently, to a certain degree, of the action of the recepte cle H. Ordinarily, the heat released by'the resistance wire 2| is of a mild character so that the electric circuit governed by the humidostat may remain closed for a desired interval of time. More rapid heating of the resistance 2| may be used, however, to produce short cycle operation of electrical apparatus disposed in the humidostat circuit.

To overcome the tendency of room temperature to cause the bimetallic strip in to effect the operation of the humidostat, the lower strip 8 is also made of a corresponding bimetal construction and set Ior opposite flexing action. In this way.

the two bimetallic strips neutralize each other so far as room temperature is concerned. If it should be desired to increase or decrease humidity with the rise or fall of temperature, the resilient bimetallic strips may be made of difierent relative size or thickness.

As shown in Fig. 2, current obtained from any suitable source, such as a commercial electric circuit, is conveyed by a conductor 22 to a terminal binding post 23 with which isv also connected one end of the resistance wire 2|. A second conductor 24 extends from the source of current supply and leads to an electrical device or devices 25, theoperation of which the humidostat is employed to control. for example, the motor of a fan employed in forcing water vapor laden air to the room or rooms in Such, a device may comprisey which the htunidostat is disposed, or the device 25 may comprise an electrically actuated valve, control switch, or the like. From the device 25, the conductor 24 extends to a second terminal post 26, and from this post, a conductor 27 extends upwardly through the back of the base section 2 in order that its upper end may be connected with the strip IE or the armature Hi.

In view of the foregoing, it will be evident that the present invention provides a humidostat in which the operating principle resides in the utilization of the change in weight of the moisture absorbent material contained in the receptacle ll to operate an electric switch. The structure employed in accomplishing this end is simple, rugged and efllcient. If it should be desired to replace or repair parts, the removal of the cover section provides for complete accessibility, and by a sliding movement the internal parts may be readily moved into or out of position. It will be noted that the receptacle II is mounted at its ends on bimetallic spring strips having flexing characteristics which are such as to prevent the temperature of the room atmosphere from effecting the operation of the receptacle. By the use of the magnet, the operation of the humidostat is stabilized with respect to the matter of maintaining the electric circuit associated with the switch in a positively closed condition, overcoming any tendency of the humidostat to set up a fluttering circuit operation. However, in order to overcome the adhering attraction of the magnet for the armature, and to impart operating cycles of definite duration to the associated electrical apparatus involved in the hurnidostat control circuit, the electric heater produces positive flexure of the bimetallic strip IO which, when heated to a desired degree, flexes with tension, so that when suflicient tension is developed, the magnet is separated from the armature with a snap action, preventing destructive arcing between the contacts I! and i3.

Obviously, any number of contacts may be provided to suit particular requirements without departing from the spirit of the invention.

I claim:

1. A humidity responsive switch comprising a casing, an air permeable receptacle containing a water vapor absorbing material mounted for movement in said casing, bimetallic strips having their flexible intermediate portions connected with said receptacle, said strips being of the character to neutralize the effect of variations in temperature on each other with respect to operational movement of said receptacle, and circuit completing and interrupting means actuated by movement of said receptacle in response to changes in its effective weight.

2. A humidity responsive switch comprising a casing, an air permeable receptacle containing a water vapor absorbing material, thermostatic means carried by the casing for the support of said receptacle, a magnet having a contact movable in unison with said receptacle, an armature mounted within said casing in registration with and in spaced relation from said magnet, a contact carried by said armature adapted to be i broughtdnto and out of engagement with the magnet contact, and means carried by said casing for regulating thev spacing between said armature and magnet.

3. A humidity responsive switch comprising a casing, a receptacle containing a water vapor absorbing medium, a pair or bimetallic strips supported at their ends within said casing and having their intermediate portions disposed in-conneonate tact with the ends oi said receptacle, one of said strips being adapted to flex downwardly and the other oi said strips upwardly when the same are warmed, whereby to neutralize the effects of room temperature variations on said receptacle, and circuit completing and interrupting means actuated by movement oi said receptacle in response to changes in its effective weight.

4. A humidity responsive switch comprising a casing, a receptacle containing a water vapor absorbing medium, spaced bimetallic strips supported at their ends within said casing, the intermediate portions of said strips being disposed in contact with the opposite ends of'said receptacle, one of said strips being of a character to flex downwardly when heated, and the other of said strips being adapted to flex upwardly when heated, means independent of room temperatures for locally heating one of said strips, a permanent magnet movable in unison with one of said strips, and an armature adjustably supported in said casing in appropriately spaced relation from said magnet, said magnet and armature being provided with registering circuit making and breaking contacts.

absorbing medium, resilien 5. A humidity responsive switch c casing, a receptacie conta" carried by said casing for the app ceptacle through engager with ends thereof, a magnet hay g a con 0 mr in unison with said receptacle, an adjus mature mounted within said casing in regis a= tion with said magnet, said armature being pro vided with a contact disposed for engagement with the contact of said magnet, and. eiectricaliy energized means for locally heating the resilient receptacle supporting means.

6. A humidity-responsive switch comprising a casing, a Water vapor absorbing element movably mounted in said casing, resilient thermostatic devices mounted in said casing to effect the support of said element by engagement with the opposite ends thereof, said devices serving to neutralize the effects of temperature variation with respect to each other in the support of said element, and circuit completing and interrupting means actuated by the movement of said element in accordance with changes in its efiective weight.

GEORGE W. CRISE, 

